1. Field of the Invention
This invention relates to a photothermal and/or a photochemical process induced by laser radiation to destroy hair follicles and to prevent hair growth after traditional hair stripping.
2. Invention Disclosure Statement
Techniques for removal of unwanted hair have traditionally been electrolysis and chemical or wax depilatories. Such techniques, when used by themselves, must be repeated several times to ensure a semi-permanent effect. Thus, these techniques used alone consume excessive time and expose the patient to repeated painful treatments.
As an alternative to these conventional treatments, lasers have also been used to remove unwanted hair with significant benefits. Many problems still exist, however, with state of the art hair removal systems. The most significant problems are low permanent hair removal percentage and complexity of operation.
U.S. Pat. No. 5,425,728, xe2x80x9cHair Removal Device and Methodxe2x80x9d, Tankovich, describes a system of permanent laser hair removal. After shaving the hairs in a treatment area to a height of 1 mm above the skin, hair on a section of skin is contaminated with a carbon oil substance having high absorption of a frequency band of light. The skin is illuminated with light at this frequency band by a Nd:YAG laser at sufficient intensity and duration to kill the follicles or the skin tissue feeding the hair. This is carried out by either photothermal or photochemical reactions. After the laser treatments, a 30% hair reduction resulted. The problem with this invention is that it is difficult for the carbon oil absorber to penetrate to the depth of the hair follicle while the hair is still in place. Another problem is low percentage hair reduction.
The problem of penetration was addressed in a later patent by Tankovich, Zhao, and Fairchild. U.S. Pat. No. 5,752,949 entitled xe2x80x9cHair Removal Methodxe2x80x9d which describes a method whereby photosensitizers are activated in two distinct phases. In a xe2x80x9cmechanicalxe2x80x9d phase, the skin section is illuminated (e.g. by a laser) with at least one short pulse of light sufficient to cause tiny explosions in the contaminant forcing portions of the contaminant more deeply into the hair ducts. During a xe2x80x9cthermalxe2x80x9d phase the skin section is then illuminated so as to heat the contaminant substantially without further explosion or vaporization of the contaminant. This is a complicated means of achieving hair duct penetration.
Yet another patent by Tankovich, et al, U.S. Pat. No. 5,752,948 also entitled xe2x80x9cHair Removal Methodxe2x80x9d further addressed the problem of hair duct penetration. In one embodiment of this patent, the hairs in the section of skin being treated are pulled out prior to application of the contaminant so as to provide more space for the contaminant in the hair duct. In another preferred embodiment, a portion of the hairs below the skin surface is removed with a depilatory. Admitting that effective permanent hair removal largely depends upon good penetration of the photosensitizer into the hair duct, this patent attempts to offer solutions to this problem. However, this invention does not allow for chemically acting photosensitizers to be used. It also makes use of carbon particulate matter, not a smooth lotion for application of photosensitizers. It is more difficult for the carbon particles to penetrate to the depth of the follicle because of their particle size. Lastly, in a particularly preferred embodiment of this invention, the inventors recommend leaving the photosensitizing lotion on the surface of the skin. This practice may expose the skin surface to excessive radiation and be damaging to the skin.
The process described in U.S. Pat. No. 5,752,948 is also overly invasive. It is a photomechanical process that utilizes laser energy to raise treatment temperatures to such a degree that explosive ablation and optical breakdown occur. Such a process is unnecessary for the given result. In contrast, the present invention utilizes a continuous wave laser. The laser energy produced by the present invention does not need to raise the temperature of the treatment site higher than 70xc2x0 C. Therefore, the present invention allows us to work at more benign, less harmful temperatures.
U.S. Pat. No. 5,853,407 entitled xe2x80x9cMethod and Apparatus for Hair Removalxe2x80x9d, by Miller, has another approach to permanent laser hair removal. This invention uses pulsed coherent light of selected wavelength and peak power level and post duration, and repeating the coherent laser irradiation on one or more subsequent occasions with selected light parameters. The specific target for laser radiation described in this disclosure is the melanin within the hair shaft and within the melanocytes lining the follicular duct. Targeting melanin with radiation, however, has the undesirable side effect of changing skin pigmentation. This invention is overly complicated and time-consuming because it requires two or more radiative treatments to be performed with a healing time of 1-3 months between each treatment.
Yet another means of permanent laser hair removal is found in U.S. Pat. No. 5,846,252 entitled xe2x80x9cMethod of Removing Hair from the Body and Inhibiting Future Growthxe2x80x9d, by Mehl. This patent describes a method for the removal of hair through the use of electromagnetic (e.g., AC, DC, blend, and laser) energy by treatment of the hair prior to the application of such electromagnetic energy to reduce the electromagnetic energy resistance of the hair. This electrochemical removal process does not provide for hairs to be removed prior to irradiation since in this invention the hair itself is used to conduct electricity into the follicle. This method is very time-consuming because it requires individual removal of hair.
In U.S. Pat. No. 5,489,279, by Meserol and assigned to DUSA Pharmaceuticals employs light-activated topical photopharmaceutical 5-ALA (a drug used to treat cancer in PhotoDynamic Therapy, available from the Sigma Chemical Company, St. Louis, Mo.), to photochemically oxidize and thus destroy proliferous cellular components of the follicle.
Thus, state of the art laser hair removal methods offer improvements over more conventional methods. They can be relatively quick and painless operations. They still have drawbacks, however. The main drawback is that all of the above techniques have a low permanent hair reduction percentage. Another common drawback to many of these techniques is that the hair and the follicle must be destroyed by the radiation. Thus, more body tissue must be destroyed by radiation. Furthermore, many state of the art hair removal systems involve radiation of melanin which causes depigmentation, an undesirable side effect. Additionally, state of the art laser hair removal techniques propose the use of overly complex and expensive lasers.
Diode lasers possess many advantages when compared to other types of lasers, including Nd:YAG and ruby lasers, as mentioned above. They are efficient, inexpensive, compact and easy to operate and maintain.
Thus, a hair removal system that provides the advantages of a low cost diode laser with improved permanence of hair removal, low residual melanin absorption to avoid depigmentation at the treatment site, and a short treatment period is needed.
It is therefore the aim of the present invention to provide a laser hair removal method which addresses these shortcomings.
It is an object of the present invention to provide a method for permanent hair removal using a diode laser system to avoid the complexities of state of the art laser hair removal systems.
Another object of the present invention is to provide a method for permanent hair removal whereby hair is first removed by conventional stripping means before laser radiation is applied, to prevent excessive tissue damage.
Yet another object of the present invention is to provide a method for permanent hair removal whereby a photosensitizer is used to absorb laser radiation and aid in the destruction of hair follicles.
Still another object of the present invention is to provide a means for permanent laser hair removal using photochemical and/or photothermal processes.
A further object of the present invention is to provide a means for permanent laser hair removal which does not require long treatment periods or waiting periods between treatments.
Another object of the present invention is to provide a means for permanent laser hair removal with minimal melanin absorption ensuring that any detrimental pigmentation effects are minimized or reduced, contrary to treatments using prior art methods.
Briefly stated, the present invention provides a means to permanently remove unwanted hair using a diode laser or other laser source in a post-treatment mode. The hair in the treatment area is first removed using conventional stripping techniques leaving the hair follicles substantially empty. While the follicles are open, a special photosensitizing lotion is rubbed into the skin and until it penetrates into the depth of the follicle. A solvent is used to clean the surface of the skin from excess photosensitizer, leaving the photosensitizer in the follicles. In this way, the follicular ducts are selectively sensitized. The follicles are then irradiated by a diode laser in the near IR range and the follicles are thereby killed. There is no waiting time necessary in between different steps of treatment and only one application of laser radiation is generally required. Also, the present invention can operate through the activation of chemically acting or thermally acting photosensitizers.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numbers in different drawings denote like items.